Circulating fluidized beds are widely used in petroleum, chemical industry, metallurgy, energy, environmental protection and other industrial fields. In circulating fluidized beds of prior art, due to a high concentration of particles, less gas-solid back-mixing and easy to build up temperature and concentration gradients, not only a gas-solid contact efficiency is improved, but advantages such as easy to scale up, able to process viscous materials, higher efficiency of raw materials or equipments, less power consumption, lower investment and cost are obtained. Therefore, an effective means for improving fluidization quality and gas/solid flow performance in circulating fluidized beds of prior art is to add internal components or internals therein. The Internals used at present in fluidized beds include baffle screens, baffle plates, vertical tube bundles, etc. The internals are known in various embodiments, e.g. in a form of a ring, blunt body, round-bar structured packing, slanting flap, corrugated structure, perforated plate, remiform or ridge.
Vertical tube bundles functioning as heat exchange tubes are often used as said internals in fluidized bed reactors in foreign countries, and equivalent diameter is recommended as the scale-up index. In a domestic market, a horizontal louver baffle plate is used in combination with a heat exchange tube bundle. The above-mentioned members have different characteristics, i.e. the horizontal baffle plate has a function of breaking air bubbles, whereas the vertical tube bundle has less scale-up effect. One common defect for said two members is that they would be operated only when an empty bed velocity is lower, resulting in a gas layer containing a small amount of particles present below the horizontal baffle plate, and thus “slugging” among the vertical tubes bundles, when the gas velocity exceeds a certain value (Jin Yong, etc., “A new internal used in a fluidized bed reactor” in the Chinese patent for invention CN 85100040A). Perforated-plate internals, remiform internals and perforated-remiform internals may enhance the gas-solid mixing and contact, and thus the efficiency of a chemical reactor can be enhanced. However, due to a higher flow velocity of the gas and solid in a circulating fluidized bed and the lack of guidance of the gas flow in a fluidized bed by said internals, it is possible to increase the abrasion of said internals and the bed pressure drop in the fluidized bed, with the actual work efficiency of the fluidized bed being affected.